Magneto telephone



Aug.2s,192s. 1,550,194

R. D. FAY

MAGNET() TELEPHONE Filed April 13'. 1922 Patented Aug. 25, 1925.

UNITED STATES PATENT OFFICE.

RICHARD D. FAY, OF N AHANT, MASSACHUSETTS, ASSIGNOR, BY MESNEASSIGNMENTS, TO HAMMOND V. HAYES, TRUSTEE, OF BOSTON, MASSACHUSETTS.

MAGNETO TELEPHONE.

Application led April 13, 1922. Serial No. 552,325.

T0 all whom t may concern.'

Be it known that I, RICHARD I). FAY, of Nahant, in the county of Essexand State of Massachusetts, a citizen of the United States, haveinvented a new and useful Improvement in Magneto Telephones, of whichthe following is a specication.

I will take the case of an electro-magnetic telephone as the simplestillustration of the application of my invention to a practical anduseful p-urpose. It is well known that a telephone when used as areceiver must transform the alternating currents which are made to passthrough the coil or coils of its electro-magnet into a to-and-fromovement of a member which will produce the compressional waves in airwhich are called sound. The best receiver is one which will make thistransformation from electrical waves into air waves with the leastpossible loss in energy and will at the same time create sound waves asnearly as possible similaiin form and relative intensity as theelectrical waves which actuate it. Similarly when the telephone is usedas a transmitter for transforming air waves into electrical waves, thebest form is that in which there is the least loss of energy in thetransformation and in which there is the least distortion in electricalwave form from that of the actuating air wave form.

Or, if the case of a quick-acting relay is considered, the design mustbe such as will offer the least possible loss or deformation of theincoming electrical wave and at the same time create a motion of themoving part as quickly as possible and with the least possible loss ofenergy.

The well known form of Bell receiver does not meet the requirements.outlined above, both on account of its high effective resistance andfrom the fact that there are large losses in the magnetic circuitarising from the necessity of having a thin diaphragm, forming a portionof the magnetic circuit, and considerable separation between the polepieces and the diaphragm. I am aware that attempts have been made toovercome these difficulties by the elimination of the diaphragm as aportion of the magnetic circuit as has been done by supporting from thediaphragm a light coil or a tube of conducting material, said coils ortubes moving in a powerful magnetic field. The weight of these movingparts and the large air gap required in the magnetic field has resultedin little or no improvement in.`

the sensitiveness of such devices when used as telephone receivers,although instruments of this type have one important advantage m thatthe amplitude of the moving parts is restricted only by the flexibilityof the diaphragm to which they are attached.` I am aware that anothertype of receiverl has been devised in which an armature, piv-j cted orhinged between the two poles of a` magnet or electro-magnet, is used,such argreater amplitude of motion of the soundff.I

energy.

My invention consists in an electro-magnet in which the armature isnormally substantially under no strains such as are imposed by springsor similar means and is free to move in a substantially uniform fieldwith unrestricted amplitude as far as the magnet is concerned.

The armature of my electro-magnet, when no alternating current is actingupon it, is so balanced that there is no resultant longitudinal pullupon it.

In the drawings accompanying the present specification my invention isshown in its preferred form.

Figure 1 s a front elevation of my electromagnet.

Fig. 2 is a section on line Qf-EZ of Fig. 1.

Fig. 2L is a modification.

Fig. 3 shows the armature of my electromagnet as blanked out.

Fig. I is a sectional view of a casing enclosing my electro-magnet whenused in a magneto telephone.

Fig. 5 is a plan of my electro-magnet.

1 is a spool of insulated wire for carrying the alternating currentsused when the electro-magnet is actuated, its leads l(not shown) CIIbeing connected with a suitable source of alternating current. 2 and 3are pole pieces which pass, respectively, over and under the spool (seeFig. 2), being connected to the horse-shoe magnet M by bars 2l and 8l.(S is the armature which is a thin plate ot iron or high permeabilitywhich passes through the central opening in said spool l. This armatureis punched or blanlied as shown in Fig. 3 and then bent into the tornishown in F ig. -1. rEhe metal removed inales a reetangular hole at 7,leaving two nai-ron` strips at 8 and 9,1 and when the armature is bentinto the form shown in Q, it the end ll is held lirmly and pressureapplied at the end l0, the strips will bend easily thus form practicallya spring hinge for the armature. rllhus the ond l0 has D dom oitmovement while there is relatively small movement ot the armature atpoints where the strips 8 and i) the main body of the armature 6. Thebent end ll of the armature is held rigidly upon one et the pole piecesby 'four screws l2, 13, and l5. Screw l2 is tapped into the pole pieceand screws 18, and l5 are tapped into the part ll, their ends resting`against the pole piece.

The pole pieces Q ant 3 are extensions ot magnet M, and as shown areshaped to substantia-lly surround the coil and form a row slit in whichthe armature in u "'ibratd the edges 4l and 5 being chain'rered to direet the magnetic linx onto the armature.

An important feature orn my invention lies in the relation which is madeto exist between the pole pieces and the armature. To illustrate th'srelation, Fig. 2 is presented which is a oross section at Qr-Q of li.See, also, lEig. 2l which shows the armature blank arranged in relationto one ot the pole pieces. lt will be seen that armature 6 can bebrought into the closest proximity to the surfaces and of the polepieces and, as the pole pieces are slotted as at a; to allow theprojection l0 move freely, the armature can travel to points within theChamber enclosed by the pole pieces, but it is so proportioned withrelation to the pole pieces that it will not touch them eren when itsmovements are. the greate a result of this design the magneti( ill; sbetween 6 and 2, 3, et and are subst and as a consequence there is nolonsri strain exerted ipon (l by t pole faces. Moreover, the through thearmature ar practically nnmagnetized longitudinally and as a consequencethe lai i st ssible i of lines of 'force will be induced in it by thealternating currents when L assing through tb. e

coil l. lt the alternating current at a Y. Ten instant ot tune makes thearmature horth at its ree end, it will be polarized South at the end atwhich 1t 1s pivoted.

Theoretically strips 8 and 9' should be of non-:nagnetie n'iaterialv`bnt for mechanical reasons l bave preferred to use the same ma- 'forthese strips as that used in the "are and to eli. `inate losses byreducthe e e sections et the stri*L to a miniconsistent with therequisite mechani- TKT i i ln i the gen-ral arrangement of mybloemmagnet as :rpg-lied to a telephone re- I is chown. Y i thisorar-:ing 16 is a A .'YX! AL Stlll.

2C has one enc secured to l`he other end et the rod is attached and Thusnre are imparted be a permanent or elecdesired and other changesnfnetion shown in the drawbe made without departing fron "ter oi" myclaims renten is particularly adapted to nets in such forms as are usedting relays. 'found that a very etlicient way ot ing the armature isthat shown in j Q5 where as shown at 32 a piece o' ,stic material suchas sott rubber is placed between the armature and the pole piece and asecond like pi ce ot material is placed outside the armature. is a metalQiece or Yasher. il screw 2 A asses through this washer and tao members3; as well as through the armature and holds the armature to the polepiece.

lVhat claim as my invention is:

fr device of the lind described Compris! ing a lield magnet having polepieces located to ,torni two short air gaps in the magnetic eii mit, nis ttor supporting an armature attaened at one end to said l support eanswhereby its other end may swing k A-- 7 sait pole pieces being locatedon opposite side armature be" f 3. ln a device of the kind described,magnet the poles of which are located to form two gaps of differentlength in the magnetic path, an armature located between said gaps withone end projecting into the longer of said gaps and with the other endoverlapping the pole pieces at the shorter gap, said armature beinghinged near the projecting end.

4. In a device of the kind described, an electro-magnet responsive toalternating currents, having a normally longitudinally uninagnetizedarmature pivotally mounted near one end thereof, a field magnet, theother end of said armature being located in close proximity to two polefaces of said field magnet of opposite polarity, said pole faces andsaid other end of said armature being shaped with relation to each otherwhereby said armature may be given an amplitude of vibrationmechanically unrestrained by said poles.

5. An electro-magnet having an armature hinged nearmoneend, analternating current coil located to surround kthe free portion of saidarmature, afield magnet having recessed pole pieces located to partiallyenclose said coil, the free end of said armature being proportioned tovibrate within the recesses in said pole pieces.

6. A magneto-telephone comprising a diaphragm and means by which it isactuated comprisinga magnet and an armature, said magnet comprising acoil located between the two pole pieces of said magnet, said polepieces being in close proximity to each other, one end of said armaturebeing attached to one of said pole pieces and the other end thereoflying within the coil and between the surfaces of said pole facesadjacent to the coil.

7. A field magnet, an armature, a mounting therefor engaging one endthereof Whereby the other end of said armature is free to vibrate, acoil surrounding said armature, the poles of said magnet being recessedand said armature being located to vibrate within said recesses.

8. A magneto-telephone comprising a diaphragm and means by which it isactuated comprising a magnet and an armature, said magnet comprising acoil located between the two pole pieces of said magnet, said polepieces being in close proximity to each other, one end of said armaturebeing attached to one of said pole pieces and the other end thereoflying within the coil and between the surfaces of said pole facesadjacent to the coil, said armature-attracting means comprising a clamphaving two pieces of soft elastic material, one located on each side ofsaid end and means for clamping said elastic material and said end toits pole piece.

RICHARD D. FAY.

